The present invention generally relates to resilient cushions, and more particularly relates to a simulated gel core cushion and a method of manufacture.
A recent surge in the number of wrist and arm occupational injuries, resulting from repetitive computer keyboard use, has prompted the development of countless cushions directed at alleviating this modern problem. xe2x80x9cCarpal Tunnel Syndromexe2x80x9d has become a well-known term describing a group of symptoms, including tendonitis, and epicondylitis, that occurs as a result of repetitive flexion of the wrist joints. Not only are the symptoms of Carpal Tunnel Syndrome extremely painful, they have the potential to be permanently debilitating. Fortunately, it has been found that if the causes of the disease are minimized or eliminated in time, further damage therefrom may be averted.
Some prior art wrist cushions, though designed to minimize repetitive wrist flexion, tend to be uncomfortable to use after a period of time. Notably, because such devices are typically positioned for supporting the underside of a user""s wrist, flow of blood may be impeded by the use of rigid, non-yielding material.
Thus, a number of prior art wrist cushions are comprised of softer, more comfortable materials, such as foam rubber. Unfortunately, the resiliency of foam rubber, and other similar cellular materials, tends to diminish after extended periods of use. Furthermore, foam rubber tends to wear unevenly, resulting in hardened areas where compression is most regularly applied. Thus, foam rubber supports become less comfortable with time, necessitating frequent replacement thereof.
Cushioning devices having liquid or gel filled bladders have been developed in the attempt to provide a more comfortable, more durable support for the wrist than is possible with solid or foam rubber supports. For example, U.S. Pat. No. 5,435,508 discloses a wrist rest support comprising a viscous, fluid-filled bladder removably inserted in a machine washable outer covering.
Such liquid and gel cushions are manufactured by several independent steps, including sewing or other means of assembling the bladder, filling the bladder with the desired liquid, sealing the bladder such that it will resist leakage, and fashioning an outer covering in which to enclose the liquid filled bladder. It is clear that these procedures are time consuming and, as a result, expensive.
Gel cushion provide superior resilient characteristics, however, such gels, as for example, triblock polymer, are very expensive which limits their use.
The present invention provides a substantially less complicated process for manufacturing a comfortable resilient cushion that includes all the advantages of a gel cushion.
A cushion in accordance with the present invention generally includes a sheet, or cover, and a core disposed within the cover. The core includes a volume of individual separate particulates and a liquid, such as oil, disposed between the particulates for enabling lubricated movement of the particulates within the core in response to an outside force applied to the cover. The cover may be tensioned by the core into the selected contour or the cover may be preformed into the selected contour.
As a specific example, a cushion in accordance with the present invention may include a sheet that is stretched or tensioned in a selected contour, a backing, and a core disposed between the stretched sheet and the backing.
The core may comprise a mixture of compressible particulates and a liquid. This configuration provides gel like resilient characteristics. The liquid, which may be oil, is generally incompressible, however, compressible particulates mixed therewith provide, in combination, the xe2x80x9cfeelxe2x80x9d of a gel cushion. That is, the mixture does not displace like a liquid but has an elastomer feel like a gel.
In one embodiment, the particulates may comprise open cell foam particles, and in this instance, the liquid may be at least partially disposed within the open cell foam particles. The particles, which may be partially filled with the liquid, remain compressible. The amount of open cell foam utilized is a factor in controlling the overall resilient xe2x80x9cfeelxe2x80x9d of the resulting cushion.
In addition, this feature provides for the resiliency enabled by the foam yet less liquid is free to leak from the cushion if the stretchable sheet of backing is ruptured, pierced or cracked.
In addition, to further tailor the resiliency of the foam, polymer particulates may also be distributed as part of the core mixture.
The sheet may be a formed elastomer or, a separate elastomer layer may be provided between the sheet and the core in order to both prevent leakage of the liquid from the cushion in case the sheet is ruptured and to prevent sensing by a user through the sheet of the particulates in the core. In this manner, a gel-like cushion is provided without the use of expensive gel materials.
Accordingly, a cushion in accordance with the present invention generally includes the flexible sheet and the core is produced by providing a mold having a selected contour and disposing the stretchable sheet over the mold. A volume of a mixture comprising particulates and liquid is disposed into the mold onto an exposed side of the stretchable fabric and the volume is forced into the mold to stretch the sheet to the contour. The backing is sealed on a bottom of a cushion to trap the volume between the sheet and the backing.
One embodiment of the present invention, the stretchable sheet may comprise an elastomer and the elastomer may be preshaped to the contour before insertion into the mold in order to facilitate assembly of the cushion.